THE FOUtfG N^TtTRA.L 1ST. 



359 



Hypnoruni- — This shell is longer and 

 narrower than the last, being somewhat spin- 

 dle shape, with the spire rather long and 

 pointed, and the aperture narrow and oblique ; 

 it is pale brownish, glossy, thin and semitrans- 

 parent, and has the whorls reversed, the 

 animal has not the mantle turned back over 

 the outside of the shell like Fontinalis, but 

 otherwise resembles it, having thread-like 

 tentacles with the eyes at their inner base, 

 it may be found in streams, ponds and ditches 

 throughout the country. 



Genus, Lymnaea. 



The shells of this genus vary very con- 

 siderably in form, some being long and 

 narrow, others broad and oval, they are all 

 however spiral shells with the whorls coiled 

 to the right, differing in this respect from 

 those of Pkysa which are coiled to the left. 

 The animals may be distinguished from those 

 of the preceding genera by the form of the 

 tentacles, which are flat and triangular ; the 

 eyes are at the base of the tentacles at their 

 edge. There are eight British species, Limosa, 

 Auricularia, Stagnalis, Palustris, Truncatula, 

 Glabra, Glvtinosn, and Involuta. 



LilHOSa. — This shell is somewhat oval, 

 with small raised spire and large aperture, 

 yellowish or pale brown, in color, measuring 

 from half to three quarters of an inch in length 

 when full grown, is striated in the direction of 

 of the lines of growth, it has no umbilicus, 

 the lip being turned back over this portion of 

 the shell. It is a variable shell, the spire being 

 more or less raised and the whorls more or 

 less distended in different species. The animal 

 is variable in color, brown, greenish, or grey ; 

 it has a broad head with triangular tentacles, 

 at the inner corner of which the eyes are 

 placed. This is our commonest pond snail 

 every pond, ditch and sluggish stream abound- 

 ing with them. (This species is better known 

 to collectors as L. pcreger. 



Auricularia. — The shell of this species 

 is rather larger than the last, with a small 

 raised spire ; the whorls increase rapidly in 



j size, the last being very widely expanded, and 



1 the aperture very large and ear-shaped ; it is 



; thin and pale, striated irregularly in the 



, : direction of the lines of the growth. It is not 

 so common as the last, being found only in 

 the southern and midland portions of Eng- 

 land and Ireland, in ponds, marshes, &c. 

 Stagnalis.— This is much the largest 



j shell of the genus, it has a long tapering 

 spire, rounded whorls, with compressed 



| sutures, and large aperture, it is yellowish in 



I color, striated, and rather thin. It is to be 

 found in ponds, canals, streams, &c, chiefly 

 in the southern and midland counties, 



Palustris.— This is an oval shell with a 



j conical spire, it is of moderate dimensions, 

 generally dark brown, rather solid, roughly 

 striated, the whorls increasing regularly in 

 size, the aperture comparatively small, it 

 may be found in marshes, ponds, &c, 

 throughout the country. 



Truncatula. — -V smaller shell than the 

 last, of similar shape, but paler in color, 



, being yellowish, and the sutures are more 

 marked than in Palustris, the aperture is 

 small and the whorls rounded and striated in 

 the direction of the lines of growth. It is 

 found about ponds, sluggish streams, &c. 



Glabra. — This is a very different shell to 

 any other in the genus, being long, narrow, 



j and many whorled, the spire is long and 

 conical, the aperture very small ; it is yel- 

 lowish, thin and smooth, finely striated. It 

 is found chiefly in the north and central 

 parts of England, in ponds, ditches, &c. 



GlutillOSa. — A rather small ova! shell, 



I yellow, very thin and transparent, with 

 rapidly enlarging whorls, and wide aperture, 

 the spire is raised but very small. It is a 

 scarce species, having been found in only a 

 few localities ; it lives in ponds and ditches. 



Involuta. — This shell resembles the last 

 in every respect, except that the spire is sunk 



! below the outer whorls. It is recorded as 

 being found only in one locality in Ireland, in 



j a small mountain lake. 



j (To be continued.) 



